Protective helmet



FIG. 1 is a left side view of a protective helmet showing my new design;

FIG. 2 is a right side view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a top view thereof;

FIG. 6 is a bottom view thereof (dashed lines forming no part of the design);

FIG. 7 is a left side view of a second embodiment thereof;

FIG. 8 is a right side view of FIG. 7;

FIG. 9 is a front view of FIG. 7;

FIG. 10 is a rear view of FIG. 7;

FIG. 11 is a top view of FIG. 7; and,

FIG. 12 is a bottom view of FIG. 7.

The details shown in broken lines form no part of the claimed design. 

CLAIM The ornamental design for a protective helmet, as shown and described. 